Dust Storm in Arizona, May 1, 2007

AZZ020>028-CAZ030>033-020600-

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE PHOENIX AZ
415 PM MST TUE MAY 1 2007

CORRECTED WATCHES/WARNINGS/ADVISORIES SECTION
REVISED AVIATION DISCUSSION

SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA
FORECAST DISCUSSION

.SYNOPSIS...
A LOW PRESSURE SYSTEM MOVING EAST ACROSS SOUTHWEST ARIZONA MEANS A
CHANCE OF SHOWERS AND THUNDERSTORMS WITH STRONG GUSTY WINDS IN SOUTH-
CENTRAL ARIZONA INCLUDING THE GREATER PHOENIX AREA THROUGH THIS
EVENING...AND A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ELSEWHERE.
THE LOW PRESSURE SYSTEM WILL MOVE NORTHEAST TO EASTERN ARIZONA WITH
THE CHANCE OF SHOWERS AND THUNDERSTORMS ENDING FROM THE WEST BY LATE
TONIGHT. A LARGE LOW PRESSURE SYSTEM FROM THE GULF OF ALASKA WILL
DEVELOP OVER THE WESTERN UNITED STATES WITH LOWER TEMPERATURES...AND
BREEZY TO SOMEWHAT WINDY CONDITIONS THE REST OF THE WEEK ESPECIALLY
IN SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY.
TEMPERATURES WILL BE BELOW AVERAGE FOR EARLY MAY THIS WEEKEND.

&&

.SHORT TERM...
TONIGHT THROUGH FRIDAY...
UNDER PARTLY SUNNY SKIES...TEMPERATURES WERE GENERALLY 3 TO 9 DEGREES
LOWER AND DEW POINT TEMPERATURES 3 TO 8 DEGREES HIGHER EARLY THIS
AFTERNOON COMPARED WITH THE SAME TIME YESTERDAY. THERE WERE ISOLATED
SPRINKLES AND SHOWERS...BUT MOST SHOWERS WERE DISSIPATING OVER
NORTHWEST IMPERIAL COUNTY WHERE THERE WERE ALSO ISOLATED
THUNDERSTORMS DISSIPATING....AND SOME SHOWERS DEVELOPING IN SOUTHERN
GILA COUNTY. BESIDES THOSE AREAS...LITTLE RAIN WAS REACHING THE
GROUND ELSEWHERE AS OF EARLY THIS AFTERNOON.

THE FORECAST HAS BEEN CHANGED TO INCREASE THE CHANCE OF SHOWERS AND
THUNDERSTORMS...SOME WITH STRONG GUSTY WINDS IN SOUTH-CENTRAL
ARIZONA INCLUDING THE GREATER PHOENIX AREA INTO THIS EVENING. IT
LOOKS AS IF THERE WILL BE ENOUGH MOISTURE WITH THE LOW PRESSURE
SYSTEM...AND DRY AIR NEAR THE SURFACE FOR THE POSSIBILITY OF SEVERE
OR CLOSE TO SEVERE THUNDERSTORMS WITH STRONG GUSTY DOWN-BURST
WINDS...ESPECIALLY IN SOUTH-CENTRAL ARIZONA INCLUDING THE GREATER
PHOENIX AREA THIS AFTERNOON...MAINLY LATE THIS AFTERNOON INTO THIS
EVENING.

THE LOW PRESSURE SYSTEM WILL MOVE EAST ACROSS SOUTHWEST ARIZONA
THROUGH THIS EVENING...AND BESIDES THE AFOREMENTIONED CHANCE IN
SOUTH-CENTRAL ARIZONA...THERE IS A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS IN SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA INTO
THIS EVENING.

THE LOW PRESSURE SYSTEM WILL MOVE NORTHEAST TO EASTERN ARIZONA WITH
THE CHANCE OF SHOWERS AND THUNDERSTORMS ENDING FROM THE WEST BY LATE
TONIGHT.

A LARGE LOW PRESSURE SYSTEM FROM THE GULF OF ALASKA WILL DEVELOP
OVER THE WESTERN UNITED STATES WITH LOWER TEMPERATURES AND BREEZY TO
SOMEWHAT WINDY CONDITIONS THE REST OF THE WEEK...ESPECIALLY IN
SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY. WITH THESE
WINDS IT WILL ALSO BE DRY ENOUGH FOR A FIRE WEATHER WATCH WHICH IS
IN EFFECT FOR SOUTHEAST CALIFORNIA AND THE LOWER COLORADO RIVER
VALLEY WEDNESDAY AFTERNOON AND WEDNESDAY EVENING. SEE FIRE WEATHER
DISCUSSION BELOW.

&&

.LONG TERM...
FRIDAY NIGHT THROUGH TUESDAY...
EARLY IN THE EXTENDED...THERE IS SOME MODEL AGREEMENT ON THE IDEA OF
THE LARGE TROUGH OVER THE WESTERN STATES PUSHING SOUTHWARD INTO OUR
FORECAST AREA EARLY IN THE EXTENDED. OPERATIONAL GFS HAS CHANGED ITS
TUNE FROM PREVIOUS DAYS WHEREIN IT KEPT THE SOUTHERN END OF THE MAIN
TROUGH TO OUR NORTH. GFS AND ECMWF GENERALLY AGREE NOW AND HAS SOME
SUPPORT FROM THE CANADIAN. HOWEVER...THE GFS ENSEMBLE MEAN KEEPS THE
TROUGH CENTERED WELL TO THE NORTH. LEANING TOWARD A BLEND OF THE
OPERATIONAL GFS AND ECMWF...MAIN DECREASE IN HIGH TEMPS DURING THE
EXTENDED CONTINUES TO BE SATURDAY. ALSO INTRODUCED A SMALL AREA OF
SLIGHT CHANCE POPS WITH THUNDER FOR SATURDAY AND SUNDAY...PRIMARILY
ALONG BORDER WITH SOUTHERN YAVAPAI COUNTY AS WELL AS SOUTHERN GILA
COUNTY. WITH THE OVERLAND TRAJECTORY...MOISTURE WILL BE SKIMPY. ON
THE OTHER HAND...LOOKS LIKE THERE WILL BE DYNAMICAL FORCING AND
STEEPENING LAPSE RATES...ESPECIALLY SATURDAY. TEMPS BEGIN TO REBOUND
FROM WEST TO EAST BEGINNING SUNDAY AS THE LOW FILLS IN THEN MOVES
OFF. IF THE RIDGE STARTS BUILDING IN SOONER LIKE THE ENSEMBLE MEAN
SUGGESTS...WARMING WILL NEED TO START SOONER IN SOUTH-CENTRAL
ARIZONA. AT THIS TIME OF YEAR...TEMPS WILL BE PRONE TO REBOUND
QUICKLY.

&&

.AVIATION...
UPPER LOW GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN
SOUTHEASTERN CA AND SOUTHERN AZ LATE THIS AFTERNOON INTO THIS
EVENING. CEILINGS ARE GENERALLY EXPECTED TO REMAIN ABOVE 15K FEET AT
ALL TAF SITES. WINDS MAY GUST TO 25 KT THIS EVENING...AND LOCALLY
HIGHER NEAR THUNDERSTORMS. AFTER THIS UPPER LOW DEPARTS...WINDS WILL
INCREASE AREA WIDE BY TOMORROW AFTERNOON AHEAD OF ANOTHER...STRONGER
WEATHER SYSTEM. WINDS WILL LIKELY GUST TO 30-35 KNOTS BY LATE
TOMORROW AFTERNOON IN SOUTHEASTERN CALIFORNIA. AREAS OF BLOWING DUST
AND SAND ARE POSSIBLE.

SEE TAFS PHXTAFPHX...PHXTAFIWA...PHXTAFYUM...LAXTAFBLH AND LAXTAFIPL
FOR MORE DETAILED INFORMATION.

AVIATION DISCUSSION IS NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
RED FLAG WARNING FROM LATE WEDNESDAY AFTERNOON INTO WEDNESDAY
EVENING FOR CA ZONES 230...231 AND 232. IMMEDIATE FIRE WEATHER
CONCERNS ARE ISOLATED THUNDERSTORMS ACROSS THE ENTIRE AREA LATE THIS
AFTERNOON INTO THIS EVENING. WINDS REMAIN BELOW CRITICAL THRESHOLDS
THIS EVENING. AS MENTIONED...MAIN FIRE WEATHER CONCERNS IN THE SHORT
TERM ARE STRONG WINDS AND LOW RH VALUES BEGINNING WEDNESDAY
AFTERNOON AND CONTINUING INTO WEDNESDAY EVENING IN ASSOCIATION WITH
A STRONG SURFACE/UPPER LEVEL DISTURBANCE. LOW MINIMUM RH VALUES WILL
CONTINUE ON THURSDAY AND FRIDAY ALONG WITH BREEZY CONDITIONS.
OVERNIGHT RECOVERIES IN RH WILL BE FAIR TO GOOD.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...REF FLAG WARNING FOR THE LOWER COLORADO RIVER VALLEY...FIRE
     WEATHER ZONE 131...ON WEDNESDAY FROM 3 PM TO 9 PM.

CA...RED FLAG WARNING FOR SOUTHEAST CALIFORNIA INCLUDING THE LOWER
     COLORADO RIVER VALLEY...FIRE WEATHER ZONES 230...231 AND 232...
     ON WEDNESDAY FROM 3 PM TO 9 PM.

&&

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

ELLIS/17/24/TRUEMAN

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
1110 AM MST TUE MAY 1 2007

AZZ022-023-027-028-021300-
NORTHWEST MARICOPA COUNTY-GREATER PHOENIX AREA-
SOUTHWEST MARICOPA COUNTY-
NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
1110 AM MST TUE MAY 1 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

A LOW PRESSURE SYSTEM WILL MOVE FROM NORTHERN BAJA CALIFORNIA TO
SOUTHWEST ARIZONA BY LATE THIS AFTERNOON AND THIS EVENING. THERE IS
ENOUGH MOISTURE FOR A CHANCE OF THUNDERSTORMS THIS AFTERNOON INTO
THIS EVENING. THUNDERSTORMS WILL BE FAST MOVING...AND RESULT IN A
THREAT OF STRONG DOWN-BURST WINDS TO OVER 50 MPH...AND AREAS OF
DENSE BLOWING DUST.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

DRY WEATHER IS FORECAST THIS PERIOD...ALTHOUGH GUSTY AFTERNOON WINDS
ARE EXPECTED AREA-WIDE WEDNESDAY AND THURSDAY...RESULTING IN FIRE
WEATHER DANGER.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ020-021-025-026-CAZ030>033-021300-
LOWER COLORADO RIVER VALLEY AZ-WEST CENTRAL DESERTS-
YUMA/MARTINEZ LAKE AND VICINITY-SOUTHWEST DESERTS-
JOSHUA TREE NATIONAL PARK-LOWER COLORADO RIVER VALLEY CA-
RIVERSIDE COUNTY/EASTERN DESERTS-IMPERIAL COUNTY-
1110 AM MST/PDT TUE MAY 1 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EXTREME
SOUTHWEST ARIZONA...EXTREME WEST-CENTRAL ARIZONA...SOUTHWEST
ARIZONA...WEST-CENTRAL ARIZONA...EXTREME SOUTHEAST CALIFORNIA AND
SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY AND TONIGHT

A LOW PRESSURE SYSTEM WILL MOVE FROM NORTHERN BAJA CALIFORNIA TO
SOUTHWEST ARIZONA BY LATE THIS AFTERNOON AND THIS EVENING. THERE IS
ENOUGH MOISTURE FOR A SLIGHT CHANCE OF THUNDERSTORMS THROUGH EARLY
EVENING. THUNDERSTORMS WILL BE FAST MOVING...AND RESULT IN A THREAT
OF STRONG DOWN-BURST WINDS TO 50 MPH...AND AREAS OF DENSE BLOWING
DUST.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

DRY WEATHER IS FORECAST THIS PERIOD...ALTHOUGH GUSTY AFTERNOON WINDS
ARE EXPECTED AREA-WIDE WEDNESDAY AND THURSDAY...RESULTING IN FIRE
WEATHER DANGER.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

AZZ024-021300-
SOUTHERN GILA/TONTO NF FOOTHILLS-
1110 AM MST TUE MAY 1 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST-CENTRAL
ARIZONA.

.DAY ONE...TODAY AND TONIGHT

A LOW PRESSURE SYSTEM WILL MOVE FROM NORTHERN BAJA CALIFORNIA TO
SOUTHWEST ARIZONA BY LATE THIS AFTERNOON AND THIS EVENING. THERE IS
ENOUGH MOISTURE FOR A CHANCE OF THUNDERSTORMS THIS AFTERNOON AND
EVENING. THUNDERSTORMS WILL BE FAST MOVING...AND RESULT IN A THREAT
OF STRONG DOWN-BURST WINDS TO 50 MPH.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

DRY WEATHER IS FORECAST THIS PERIOD...ALTHOUGH GUSTY AFTERNOON WINDS
ARE EXPECTED AREA-WIDE WEDNESDAY AND THURSDAY...RESULTING IN FIRE
WEATHER DANGER.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

ELLIS